The invention relates to the method and device for generating an uniformalized laser beam profile by using an optical fiber.
The laser beam can be transferred up to far distance due to its satisfactory parallelism and focused on geometrically and optically in case said beam is brought sharply to a focus by a convex lens, by which result very high energy density concentrated on an infinitesimal area is obtainable on the infinitesmal area, and also as said beam has monchrom color as a pure mono color excluding all the other wave components and a characteristcs travelling straight without dispersion even through the prism, it is widely used for machining(material cutting, machining, drilling, welding, marking etc) or for measuring various heat properties of the industrial materials by the laser beam flash method etc.
However, in measuring heat properties of the industrial material by the laser flash method, YAG Laser or Ruby Laser under non uniformalized distribution has been used, and in case of using said beam, about 5% deviation error of the energy level during measuring thermal diffusivity results due to non uniformly heated test pieces, and further in case of machining the material by said beam such as cutting, drilling, welding, or marking the machined surface is not smooth togethr with difficulty of precise machining due to using said beam with non uniformalized profile.
Therefore in order to uniformalize an laser beam, by passing some partial laser beam through an optical fiber system and utilizing it undercondensed state at the center portion, some negative effects due to its non-uniformalization can be reduced more or less, but machining requiring more precision such as for thin plates or small components or local heat treatment is not so satisfactory as expected.
And as some different means for uniformalizing the laser beam, those of projecting the beam aslant on an optical fiber, or on bundle of the optical fiber and applying one dimensional local bendings to the optical fiber had been proposed.
However, as a method of projecting, a laser beam aslant on an optical fiber system had much energy loss in case projected on the fiber which result indicated a negligible uniformalized effect without any practical application, and also a method of projecting a beam on a bundle of fibers had not a success in the practical application due to some burning defects of the fiber along which clearance of boundary surface the beam passed through, despite consderable improvement of an uniformalization without any application.
Further, the method of one dimensional local bendings applied on an optical fiber system was found for a laser beam to be uniformalized markedly without any practical success under study only because of a bending effect due to the symmetrical bending offset each other, and further due to difficult regeneration without any determination for a clear bending condition and impossible uniformalization of high level.